Timescales between mantle metasomatism and kimberlite ascent indicated by diffusion profiles in garnet crystals from peridotite xenoliths

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dc.contributor.authorJollands, Michael
dc.contributor.authorHanger, Brendan
dc.contributor.authorYaxley, Gregory
dc.contributor.authorHermann, Joerg
dc.contributor.authorKilburn, Matt R
dc.date.accessioned2021-12-16T23:27:29Z
dc.date.issued2018
dc.date.updated2020-11-23T11:59:45Z
dc.description.abstractRare garnet crystals from a peridotite xenolith from the Wesselton kimberlite, South Africa, have distinct zones related to two separate episodes of mantle metasomatism. The garnet cores were firstly depleted through melt extraction, then equilibrated during metasomatism by a potentially diamond-forming carbonate-bearing or proto-kimberlitic fluid at 1100–1300 °C and 4.5–5.5 GPa. The garnet rim chemistry, in contrast, is consistent with later overgrowth in equilibrium with a kimberlite at around 1025±25°C and 4.2±0.5 GPa. This suggests that the rock was physically moved upwards by up to tens of kilometres between the two metasomatic episodes. Preserved high Ca, Al and Cr contents in orthopyroxenes suggest this uplift was tectonic, rather than magmatic. Diffusion profiles were measured over the transitions between garnet cores and rims using electron microprobe (Mg, Ca, Fe for modelling, plus Cr, Mn, Ti, Na, Al) and nano Secondary Ion Mass Spectrometry (NanoSIMS; 89Y, along with 23Na, Ca, Cr, Fe, Mn and Ti) analyses. The short profile lengths (generally <10 μm) and low Y concentrations (0.2–60 ppm) make the NanoSIMS approach preferable. Diffusion profiles at the interface between the zones yield constraints on the timescale between the second metasomatic event and eruption of the kimberlite magma that brought the xenolith to the surface. The time taken to form the diffusion profiles is on the order of 25 days to 400 yr, primarily based on modelling of Y diffusion along with Ca, Fe and Mg (multicomponent diffusion) profiles. These timescales are too long to be produced by the interaction of the mantle xenolith with the host kimberlite magma during a single-stage ascent to the crust (hours to days). The samples offer a rare opportunity to study metasomatic processes associated with failed eruption attempts in the cratonic lithosphere.en_AU
dc.format.mimetypeapplication/pdfen_AU
dc.identifier.issn0012-821Xen_AU
dc.identifier.urihttp://hdl.handle.net/1885/256636
dc.language.isoen_AUen_AU
dc.publisherElsevieren_AU
dc.rights© 2017 Elsevier B.Ven_AU
dc.sourceEarth and Planetary Science Lettersen_AU
dc.subjectdiffusionen_AU
dc.subjectkimberliteen_AU
dc.subjectmantle metasomatismen_AU
dc.subjectgarneten_AU
dc.subjectNanoSIMSen_AU
dc.titleTimescales between mantle metasomatism and kimberlite ascent indicated by diffusion profiles in garnet crystals from peridotite xenolithsen_AU
dc.typeJournal articleen_AU
local.bibliographicCitation.lastpage153en_AU
local.bibliographicCitation.startpage143en_AU
local.contributor.affiliationJollands, Michael, College of Science, ANUen_AU
local.contributor.affiliationHanger, Brendan, College of Science, ANUen_AU
local.contributor.affiliationYaxley, Gregory, College of Science, ANUen_AU
local.contributor.affiliationHermann, Joerg, College of Science, ANUen_AU
local.contributor.affiliationKilburn, Matt R, University of Western Australiaen_AU
local.contributor.authoremailrepository.admin@anu.edu.auen_AU
local.contributor.authoruidJollands, Michael, u4707055en_AU
local.contributor.authoruidHanger, Brendan, u4625618en_AU
local.contributor.authoruidYaxley, Gregory, u4039347en_AU
local.contributor.authoruidHermann, Joerg, u9907179en_AU
local.description.embargo2099-12-31
local.description.notesImported from ARIESen_AU
local.identifier.absfor020108 - Planetary Science (excl. Extraterrestrial Geology)en_AU
local.identifier.absfor040306 - Mineralogy and Crystallographyen_AU
local.identifier.ariespublicationa383154xPUB8811en_AU
local.identifier.citationvolume481en_AU
local.identifier.doi10.1016/j.epsl.2017.10.021en_AU
local.identifier.scopusID2-s2.0-85033663977
local.identifier.uidSubmittedBya383154en_AU
local.publisher.urlhttps://www.elsevier.com/en-auen_AU
local.type.statusPublished Versionen_AU

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